Mohd Hafiz Dzarfan Othman

High‐Performance, Anode‐Supported, Microtubular SOFC Prepared from Single‐Step‐Fabricated, Dual‐Layer Hollow Fibers

Microtubular solid oxide fuel cells (SOFCs) have been developed in recent years mainly due to their high specifi c surface area and fast thermal cycling. Previously, the fabrication of microtubular SOFCs was achieved through multiple-step processes. [ 1–3 ] A support layer, for example an anode support, is fi rst prepared and presintered to provide mechanical strength to the fuel cell. The electrolyte layer is then deposited and sintered prior to the fi nal coating of the cathode layer. Each step involves at least one high-temperature heat treatment, making the cell fabrication time-consuming and costly, with unstable control over cell quality. For a more economical fabrication of microtubular SOFCs with reliability and fl exibility in quality control, an advanced dry-jet wet-extrusion technique, i.e., a phase inversion-based coextrusion process, was developed. Using this technique, an electrolyte/electrode (either anode or cathode) dual-layer hollow fi ber (HF) can be formed in a single step. Generally, the electrolyte and electrode materials are separately mixed with solvent, polymer binder, and additives to form the outer and inner layer spinning suspensions, respectively, before being simultaneously coextruded through a triple-orifi ce spinneret, passing through an air gap and fi nally into a non-solvent external coagulation bath. In the mean time, a stream of nonsolvent internal coagulant is supplied through the central bore of the spinneret. The thickness of the two layers is largely determined by the design of the spinneret and can be adjusted by the corresponding extrusion rate, while the macrostructure or morphology of the prepared HF precursor can be controlled by adjusting coextrusion parameters such as suspension viscosity, air gap, and fl ow rate of internal coagulant. The dual-layer HF precursor obtained is then co-sintered once at high temperature to remove the polymer binder and form a bounding between the ceramic materials. In previous work, [ 4–6 ] a dual-layer HF support for microtubular SOFCs, which consisted of an electrolyte outer layer of approximately 80 μ m supported by an asymmetric anode inner layer with 35% fi ngerlike voids length, was successfully fabricated using the coextrusion and cosintering process. A single cell that was obtained after deposition

Hydrocarbon degradation and separation of bilge water via a novel TiO2-HNTs/PVDF-based photocatalytic membrane reactor (PMR)

This paper focuses on the potential of a novel flat sheet nanocomposite titanium dioxide (TiO2)-halloysite nanotubes (HNTs)/polyvinylidene fluoride (PVDF) membrane as a photocatalytic separator in the photocatalytic membrane reactor (PMR). The photocatalytic nanocomposite membrane acted the roles of both degradation and separation for bilge water. Both TiO2-HNTs photocatalyst and photocatalytic nanocomposite membranes were characterized by thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM) combined energy dispersive X-ray spectroscopy (EDX). The hydrocarbon degradation and removal efficiency of the PMR was evaluated by gas chromatography mass spectroscopy (GC-MS). It was found that 99.9% of hydrocarbons were removed by the PMR within 8 h, which is likely due to uniform distribution and high effectiveness of the TiO2-HNTs photocatalyst in the PVDF polymer matrix. The TiO2 leaching from the nanocomposite membrane during the membrane permeation was analyzed using flame atomic adsorption spectrophotometer (AAS), which recorded 1.0 ppb of TiO2 leaching in the permeate tank.

Antifouling polyethersulfone hemodialysis membranes incorporated with poly (citric acid) polymerized multi-walled carbon nanotubes

Poly (citric acid)-grafted-MWCNT (PCA-g-MWCNT) was incorporated as nanofiller in polyethersulfone (PES) to produce hemodialysis mixed matrix membrane (MMM). Citric acid monohydrate was polymerized onto the surface of MWCNTs by polycondensation. Neat PES membrane and PES/MWCNTs MMMs were fabricated by dry-wet spinning technique. The membranes were characterized in terms of morphology, pure water flux (PWF) and bovine serum albumin (BSA) protein rejection. The grafting yield of PCA onto MWCNTs was calculated as 149.2%. The decrease of contact angle from 77.56° to 56.06° for PES/PCA-g-MWCNTs membrane indicated the increase in surface hydrophilicity, which rendered positive impacts on the PWF and BSA rejection of the membrane. The PWF increased from 15.8Lm(-2)h(-1) to 95.36Lm(-2)h(-1) upon the incorporation of PCA-g-MWCNTs due to the attachment of abundant hydrophilic groups that present on the MWCNTs, which have improved the affinity of membrane towards the water molecules. For protein rejection, the PES/PCA-g-MWCNTs MMM rejected 95.2% of BSA whereas neat PES membrane demonstrated protein rejection of 90.2%. Compared to commercial PES hemodialysis membrane, the PES/PCA-g-MWCNTs MMMs showed less flux decline behavior and better PWF recovery ratio, suggesting that the membrane antifouling performance was improved. The incorporation of PCA-g-MWCNTs enhanced the separation features and antifouling capabilities of the PES membrane for hemodialysis application.

A review on the fabrication of electrospun polymer electrolyte membrane for direct methanol fuel cell

Proton exchange membrane (PEM) is an electrolyte which behaves as important indicator for fuel cells performance. Research and development (R&;D) on fabrication of desirable PEM have burgeoned year by year, especially for direct methanol fuel cell (DMFC). However, most of the R&;Ds only focus on the parent polymer electrolyte rather than polymer inorganic composites. This might be due to the difficulties faced in producing good dispersion of inorganic filler within the polymer matrix, which would consequently reduce the DMFCs performance. Electrospinning is a promising technique to cater for this arising problem owing to its more widespread dispersion of inorganic filler within the polymer matrix, which can reduce the size of the filler up to nanoscale. There has been a huge development on fabricating electrolyte nanocomposite membrane, regardless of the effect of electrospun nanocomposite membrane on the fuel cells performance. In this present paper, issues regarding the R&;D on electrospun sulfonated poly (ether ether ketone) (SPEEK)/inorganic nanocomposite fiber are addressed.

Effect of kaolin particle size and loading on the characteristics of kaolin ceramic support prepared via phase inversion technique

Abstract In this study, low cost ceramic supports were prepared from kaolin via phase inversion technique with two kaolin particle sizes, which are 0.04–0.6 μm (denoted as type A) and 10–15 μm (denoted as type B), at different kaolin contents ranging from 14 to 39 wt.%, sintered at 1200 °C. The effect of kaolin particle sizes as well as kaolin contents on membrane structure, pore size distribution, porosity, mechanical strength, surface roughness and gas permeation of the support were investigated. The support was prepared using kaolin type A induced asymmetric structure by combining macroporous voids and sponge-like structure in the support with pore size of 0.38 μm and 1.05 μm, respectively, and exhibited ideal porosity (27.7%), great mechanical strength (98.9 MPa) and excellent gas permeation. Preliminary study shows that the kaolin ceramic support in this work is potential to gas separation application at lower cost.

Novel hybrid photocatalytic reactor-UF nanocomposite membrane system for bilge water degradation and separation

This study focuses on the design and performance of a hybrid system consisting of a photocatalytic reactor and ultrafiltration permeation cell. Initially, an ultraviolet (UV) lamp was installed in the photocatalytic reactor to decompose the bilge organic pollutants in the presence of 200 ppm titanium-dioxide (TiO2). Individual hydrocarbon compounds of bilge water samples were identified by gas chromatography-mass spectrometry (GC-MS) analysis. Two types of membrane, which are a pure polyvinylidene fluoride (PVDF) membrane and PVDF/modified halloysite nanotube clay (M-HNTs) nanocomposite membrane were fabricated aiming to enhance the rejection, flux and fouling resistance for full filtration of pollutants from the photocatalytic reactor. The membranes were characterized by Fourier transform infrared (FTIR), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). Furthermore, GC-MS analysis showed that, over 90% bilge decomposition occurred by a photocatalytic reaction. The TiO2 cross-over during permeation was detected by using an atomic absorption spectrophotometer (AAS), which proved that, TiO2 rejection was more than 99% for the nanocomposite membrane. A UV- vis spectrophotometer confirmed over 99% rejection of decomposed bilge hydrocarbons via the nanocomposite membrane with 1.0 wt% of M-HNTs incorporated in the PVDF matrix.

Physicochemical and micromechanical investigation of a nanocopper impregnated fibre reinforced nanocomposite

This paper outlines the synthesis of a novel sustainable nanocomposite and the investigation of its physicochemical and mechanical properties using micromechanical models. As a novel approach, palm oil fibres were treated with freshly prepared nanocopper sols to make them strong and sustainable. Nanocopper particle impregnated strong and durable fibres were used to develop a fibre reinforced unsaturated polyester resin nanocomposite. The composite behavior was investigated systematically by using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, etc. Among all of the composites tested, the nanocopper particle impregnated strong and durable fibre (30%) reinforced unsaturated polyester resin composite was demonstrated to have the highest mechanical strength. The change of weight gain follows typical Fickian diffusion behavior. To predict the strength of the nanocomposite, standard micromechanical models were analyzed and the trends were seen as mixed success. The observed properties of the developed nanocomposites indicate that they can be considered for indoor to outdoor applications.

Co-Extrusion / Phase Inversion / Co-Sintering for Fabrication of Hollow Fiber Solid Oxide Fuel Cells

We have used a co-extrusion / phase inversion process, followed by co-sintering and then NiO reduction with hydrogen, to fabricate anode (Ni-CGO) / cerium-gadolinium oxide electrolyte (CGO) dual-layer hollow fibers (HFs) with inner diameters < 1 mm. This is the first time such dual-layer fibers have been produced as components of SOFCs, thereby decreasing the number of fabrication steps compared with single layer extrusion, while ensuring a gas-tight electrolyte layer of controlled thickness (ca. 60-80 μm). A La0.6Sr0.4Fe0.8Co0.2O3 (LSCF)-CGO cathode ca. 100 μm thick was deposited using slurry coating. Preliminary measurements of the performance of the dual-layer microtubular HF-SOFCs were made with hydrogen flowing at 5 cm min and air at 40 cm min, achieving maximum power densities of 420 W m, 800 W m and 1000 W m at 450C, 550C and 580C, respectively. A proposed stack design shows how these microtubular SOFCs could be connected in parallel to increase currents and in series for scaling up voltages, aiming at the design of practical stacks.

Role of lithium oxide as a sintering aid for a CGO electrolyte fabricated via a phase inversion technique

The incorporation of lithium oxide (Li2O) as a sintering additive has specific advantages for electrolyte membrane fabrication. However, the viability of the sintering additive to be implemented in a phase inversion technique is still ambiguous. In this first attempt, lithium was doped into a gadolinium-doped ceria (CGO) crystal structure using the metal nitrate doping method and calcined at four different temperatures, i.e. 140, 300, 500 and 700 °C. The prepared Li-doped CGO (Li–CGO) powders were analyzed by thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), N2 adsorption/desorption, and Fourier-transform infrared (FTIR). Primary results demonstrate that the calcination temperature of the Li–CGO influences the condition of the electrolyte suspension. Li–CGO calcined at 700 °C (D-700), as compared with other Li–CGO, possessed a strong interaction between the Li and CGO. The D-700 was then incorporated into the electrolyte flat sheet membrane which was prepared by a phase inversion technique. The membrane was then sintered at different sintering temperatures from 1350 °C to 1450 °C. In comparison with the unmodified CGO, the morphological results suggest that the Li2O can remarkably promote the densification of CGO at a lower sintering temperature (1400 °C). These findings help to promote the use of sintering additives in a ceria-based electrolyte suspension specifically for the phase inversion technique.

Development of biocompatible and safe polyethersulfone hemodialysis membrane incorporated with functionalized multi-walled carbon nanotubes

A novel approach in the design of a safe, high performance hemodialysis membrane is of great demand. Despite many advantages, the employment of prodigious nanomaterials in hemodialysis membrane is often restricted by their potential threat to health. Hence, this work focusses on designing a biocompatible polyethersulfone (PES) hemodialysis membrane embedded with poly (citric acid)-grafted-multi walled carbon nanotubes (PCA-g-MWCNTs). Two important elements which could assure the safety of the nanocomposite membrane, i.e. (i) dispersion stability and (ii) leaching of MWCNTs were observed. The results showed the improved dispersion stability of MWCNTs in water and organic solvent due to the enriched ratio of oxygen-rich groups which subsequently enhanced membrane separation features. It was revealed that only 0.17% of MWCNTs was leached out during the membrane fabrication process (phase inversion) while no leaching was detected during permeation. In terms of biocompatibility, PES/PCA-g-MWCNT nanocomposite membrane exhibited lesser C3 and C5 activation (189.13 and 5.29ng/mL) and proteins adsorption (bovine serum albumin=4.5μg/cm2, fibrinogen=15.95μg/cm2) as compared to the neat PES membrane, while keeping a normal blood coagulation time. Hence, the PES/PCA-g-MWCNT nanocomposite membrane is proven to have the prospect of becoming a safe and high performance hemodialysis membrane.